1. Field of the Invention
The present invention relates to a method of discriminating a received spread spectrum signal among a plurality of received spread spectrum signals, more particularly to determine whether or not to accept such a received spread spectrum signal on the basis of a determined statistic thereof. Such a method is particularly useful in pilot searchers of spread spectrum devices that are used in a cellular Code Division Multiple Access(CDMA) system, but the method can also be used in numerous other spread spectrum systems where there is a need to discriminate spread spectrum signals.
2. Description of the Related Art
In CDMA systems, pilot searchers are comprised in handsets. In a so-called acquisition phase, such pilot searchers search for spread spectrum pilot signals that are transmitted by radio base stations. Because such handsets typically receive pilot signals from different base stations, there is a need to discriminate a pilot signal transmitted by a particular base station. In known CDMA system, such discrimination is done by determining the total energy of the pilot signal as received by the handset. Rejection or acceptation of a pilot signal is done by comparing a statistic obtained from the received pilot signal presently under investigation with a threshold. The higher the total received energy, the higher is the value of the statistic. Therefore, to obtain predetermined probabilities of detection and false alarm when detecting pilot signals of different energies, the threshold needs to be variable.